I photograph a lot of medieval churches but never people. I do not have a no-go list as anything that produces a good picture is ok. I frequently remove items such as modern notices on walls, electric light switches, bat **** on altars and other incongruous things. I am open about doing this. In situations where I am documenting the church I do not use Photoshop at all, restricting myself to adjusting dynamic range and cropping in Lightroom. I am open about this as well.

Get rid of blemishes, rashes, flakes, noticeably out of place hairs, lint, dirt, and general grooming of the set and clothing if something was missed before I start shooting.
Fix makeup if needed.
Sometimes I liquify to get straighter lines on clothing or to sculpt hair.
Some light dodging and burning on the skin to even out the skin tones in a subtle way (still trying to figure out where to draw that line though), and sometimes to enhance the facial contour/highlights.
Brighten eyes a bit.
Whiten teeth.
Color correction and some toning, usually by using a selective color adjustment layer or curves adjustment layer.
Curves for contrast.
Sharpen.
Remove neon red skin tones from the ears, eyelids, nostrils, bridge of the nose, lips, etc.
Remove cellulite.
When it comes to stretch marks, it depends on the client or the intention of the photo.

Depends on the shoot. I have a certain level of photoshoping I would do for a typical client portrait, vs something I do when shooting a personal fun project. One, the person represents themselves and thus a reasonable amount of truth should be maintained, the other they represent a character and the concept of that character should be achieved. When it comes to the portrait I keep it reasonable. (They dont get to drop a size or two or go from a B cup to a D, but I will take out temporary scars, blemishes etc... I always ask about any prominent ones, especially in the face as some people want them removed, some want them kept and others dont care.) When it comes to a character, anything goes.

Every photo is different. I have no "absolutes"! NO always shoot raw, no always shoot in Manual, NO Absolutes.
Each shot is different just as each Photoshop effort is different.
Well, I won't do anything illegal, like add a signature to a document. Also won't make unethical changes to Real Estate photos.

I used to be a photographer in the film only days. I recognize there is this wide gray line between being a photographer and being a digital artist. For me, I arbitrarily decided not use Photoshop tools beyond what I would normally do in a wet darkroom.

I'm with Gary, they either want a photographer or a disney cartoon, minimal PS on pretty much everything though I have taken the odd head from one photo to place on a more aestetically pleasing one where the bride decided to pull a mug at precisely the wrong moment lol.

I do very little in Photoshop itself (with an exception that I'll address in a minute). I mostly shoot film, and mostly black and white, so I tend to use it for basic photo retouching (blemishes, dust, etc.) of scans from negatrives: the kind of thing that I do with a brush and dye on a silver-gelatin print.

I do most of my actual image processing in Lightroom. And there, I only adjust things that I could adjust in the darkroom -- contrast, exposure, etc. -- and stay away from the more invasive filters and features (mostly).

But that's for photography, qua photography. I see my art as something I do primarily with the camera, leading up to the point where I hit the trigger. This is as true (for me) with still life and landscapes as for portraits. I guess I fell in love with the work of Paul Strand, Andre Kertesz, and the rest, and the idea of straight photography, and decided long ago that that's what I want to do with my art.

Having said all this, graphic and web design pays more of my bills. (It's nice to sell prints, but I can't bu groceries or pay my rent with it!) And there, I will do it Photoshop whatever I need to do, and whatever my client (or a particular project) demands, from filters to colour to composites... But I tend to think of this as more of a function of prepress and publishing than photography.